React is native.
It's a JS interpreter on a separate queue rendering native UILabels and UIViews.
I'd say the concept is far more superior to UIKit which disgusts me, and I've worked with for almost seven years now. I honestly think React is the future, but for now we can try to stick with MVVM and RxSwift ;-).
I think you're fundamentally not understanding how React (not just React-native) works.